Pretty or Sweet

The grocery-store tomato that looks beautiful but tastes like tart cardboard arises from selection processes favoring phenotypes that make commercial production more reliable. Significant in that selection process was a mutation that reduced the mottled color variations of unripe green tomatoes, leaving them a uniform, pale, green. Powell et al. (p. 1711) analyzed the molecular biology of the mutation. The uniform ripening mutation turns out to disable a transcription factor called Golden 2-like (GLK2). GLK2 expression increases the fruit's photosynthetic capacity, resulting in higher sugar content.